2026 ICD-10-CM Diagnosis Code T33.71XASuperficial frostbite of right knee and lower leg, initial encounter

ICD-10-CM Codes›S00–T88›T33-T34›T33

ICD-10-CM T33.71XA
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

T33.71XA is a billable ICD-10-CM diagnosis code for superficial frostbite of right knee and lower leg, initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 922 through 923. Coders also document this condition as frostbite of knee. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Effect of other external causes, initial encounter.

Code Identity

ICD-10-CM Code
T33.71XA
Billable Status
Yes — Valid for Submission
Code Describes
Superficial frostbite of right knee and lower leg, initial encounter
Short Description
Superficial frostbite of right knee and lower leg, init
Parent Code
T33.71
Superficial frostbite of right knee and lower leg

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionT33-T34Frostbite
CategoryT33Superficial frostbite
This CodeT33.71XASuperficial frostbite of right knee and lower leg, initial encounter

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Frostbite of knee
  • Frostbite of lower leg
  • Frostbite of right knee
  • Frostbite of right lower leg

Coding GuidelinesGuidance

The appropriate 7th character is to be added to each code from block Superficial frostbite (T33). Use the following options for the applicable episode of care:

  • A - initial encounter
  • D - subsequent encounter
  • S - sequela

Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2026, published by CMS and the National Center for Health Statistics.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR INJ021
Effect of other external causes, initial encounter
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Frostbite

Frostbite is an injury to the body that is caused by freezing. It most often affects the nose, ears, cheeks, chin, fingers, or toes. Frostbite can permanently damage the body, and severe cases can lead to amputation.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert T33.71XA to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
991.3 Frostbite NEC/NOS
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About T33.71XAOverview

Is T33.71XA (Superficial frostbite of right knee and lower leg) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report superficial frostbite of right knee and lower leg, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What does the 7th character A in T33.71XA mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for superficial frostbite of right knee and lower leg, such as an emergency visit or first evaluation.

What MS-DRG does T33.71XA group to?

When superficial frostbite of right knee and lower leg, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 922, 923, with relative weights from 1.0177 to 1.7494 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of T33.71XA?

Under the General Equivalence Mappings, superficial frostbite of right knee and lower leg, initial encounter converts to ICD-9-CM 991.3 (frostbite NEC/NOS). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.